Android room数据库使用详解
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2022-03-02 21:01:31
1、引入库 def room_version = "2.3.0" implementation "androidx.room:room-runtime:$room_version" //...
1、引入库
def room_version = "2.3.0" implementation "androidx.room:room-runtime:$room_version" // for kotlin use kapt instead of annotationprocessor annotationprocessor "androidx.room:room-compiler:$room_version" // optional - rxjava2 support for room implementation "androidx.room:room-rxjava2:$room_version" // optional - rxjava3 support for room implementation "androidx.room:room-rxjava3:$room_version"
2.appdatabase类
@database(entities = { //用户信息 userinfo.class }, version = 1, exportschema = false) public abstract class appdatabase extends roomdatabase { private static appdatabase instance; public static synchronized appdatabase getinstance(context context) { if (instance == null) { instance = room.databasebuilder(context, appdatabase.class, //数据库存放在sd卡 fileutils.getdatabasepath("test.db")) //.addmigrations(migration_1_2) .build(); } return instance; } public abstract roomdao roomdao(); //进行数据库升级 static final migration migration_1_2 = new migration(1, 2) { @override public void migrate(@nonnull supportsqlitedatabase database) { //在这里用sql脚本完成 database.execsql("alter table user add column flag integer not null default 1"); } }; }
public class fileutils { public static void deletefile(string filename) { file file = new file(filename); if (file.exists()) file.delete(); } /** * 获得数据库路径,如果不存在,则创建对象对象 * * @param name */ public static string getdatabasepath(string name) { //判断是否存在sd卡 boolean sdexist = android.os.environment.media_mounted.equals(android.os.environment.getexternalstoragestate()); if (!sdexist) {//如果不存在, log.e("sd卡管理:", "sd卡不存在,请加载sd卡"); return null; } else {//如果存在 //获取sd卡路径 string dbdir = android.os.environment.getexternalstoragedirectory().getabsolutepath(); dbdir += "/database";//数据库所在目录 string dbpath = dbdir + "/" + name;//数据库路径 logutil.d("dbpath:" + dbpath); return dbpath; } } }
3.用户表
@entity(tablename = "user") public class userinfo extends basebean { @nonnull @primarykey private string userid; private string name;//用户名 private string headimg; private string pwd; private string createtime; @ignore private boolean isselect; public userinfo() { } @ignore public userinfo(string userid, string name, string headimg, string pwd) { this.userid = userid; this.name = name; this.headimg = headimg; this.pwd = pwd; } public string getuserid() { return userid; } public void setuserid(string userid) { this.userid = userid; } public string getname() { return name; } public void setname(string name) { this.name = name; } public string getheadimg() { return headimg; } public void setheadimg(string headimg) { this.headimg = headimg; } public string getpwd() { return pwd; } public void setpwd(string pwd) { this.pwd = pwd; } public boolean isselect() { return isselect; } public void setselect(boolean select) { isselect = select; } public string getcreatetime() { return createtime; } public void setcreatetime(string createtime) { this.createtime = createtime; } }
4.roomdao
@dao public interface roomdao { /** * 插入用户 * * @param user */ @insert void insertuser(userinfo user); //如果插入的新数据在表中已经存在,即如果遇上数据冲突的情况,新数据直接替换旧数据; @insert(onconflict = onconflictstrategy.replace) void insertuser(userinfo... user); @update void updateuser(userinfo note); /** * 获取所有的用户 * * @return */ @query("select * from user") livedata<list<userinfo>> getuserlist(); /** * 根据用户名查询用户 * * @param username * @return * @query("select * from user where name = :username limit 1") livedata<userinfo> finduserbyname(string username); /** * 根据userid查询用户 */ @query("select * from user where userid = :userid limit 1") livedata<userinfo> finduserbyid(string userid); }
5.repository
public class repository { private final appdatabase appdb; public repository(context context) { appdb = appdatabase.getinstance(context); } /** * 插入用户 * * @param user */ public void insertuser(final userinfo user) { new asynctask<void, void, void>() { @override protected void doinbackground(void... voids) { appdb.roomdao().insertuser(user); return null; } }.execute(); } /** * 获取所有的用户信息 * * @return */ public livedata<list<userinfo>> getuserlist() { return appdb.roomdao().getuserlist(); } /** * 根据用户名查询用户 */ public livedata<userinfo> finduserbyname(string name) { return appdb.roomdao().finduserbyname(name); } /** * 根据userid查询用户 */ public livedata<userinfo> finduserbyid(string userid) { return appdb.roomdao().finduserbyid(userid); } }
6.使用
repository repository = new repository(context); repository.getuserlist().observe(this, new observer<list<userinfo>>() { @override public void onchanged(list<userinfo> userlist) { muserlist = userlist; logutil.d("muserlist个数:" + muserlist.size()); if (muserlist.size() > 0) { madapter.setlist(userlist); } } });
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